Within the United States of America, all law enforcement is bound by their respective state Constitutions and the U.S. Constitution — 4th amendment:

Amendment IV

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Briefly; (note, this is not legal advice, and I may leave a minor step out as I am drafting this from memory) when law enforcement obtains or receives credible information, that is not in violation of the 4th amendment above, the procedure outlined next is followed;

• law enforcement (federal or state officials) may draft an affidavit for a search warrant to conduct a search of “persons, houses, papers, and effects,”
• The affidavit and warrant shall describe specific articulable facts which are evidence of a crime, how the facts were obtained, and why the fact giver is credible.
• The specific articulable facts of a crime, must be learned of legally.  Future lawful activity cannot cure previous illegally obtained evidence and/or evidence gained as a result of the illegal activity.  This is not a chicken or egg, circular argument.  Remember the words, “shall not be violated”.
• Once drafted:  The law enforcement official with knowledge of the investigation shall present the affidavit for search warrant and the warrant to a magistrate. or Judge, and then give “sworn testimony”, ie. testify under Oath or by affirmation, just as in open court.  The officer literally raises his/her right hand and takes an oath, or affirms, all the information in the affidavit is true and correct to the best of his/her knowledge.
• After the law enforcement officer swears under oath, with threat of criminal perjury for lying, the judge reviews the search warrant affidavit and if the words contained in the affidavit show legally obtained evidence of a crime, the Judge signs the warrant, allowing the officers to search a: “particularly describing the place to be searched, and the persons or things to be seized.”
• The search warrant must be acted upon quickly, a day or two, or three, otherwise the facts contained therein become stale, and the search warrant becomes invalid.
• The law enforcement officers who “serve” or “execute” the search warrant are required to file an “inventory” with the Judge/court who signed the warrant, listing all of the particular items of “evidence of a crime” seized.

Why are all the things above done by law enforcement in financial crimes, drug deals, murders, or child pornography cases?  So there are checks and balances to ensure law enforcement abides by “the law”, The Constitution, and all individual’s liberties are protected.

If a person is charged with a crime, (by indictment), the defendant and their attorney, are entitled to:

• the search warrant affidavit,
• the signed search warrant, and
• the inventory.

The defendant, through his attorney may Constitutionally challenge in front of a “neutral” magistrate, a Judge who did not sign the warrant, that “the law, and Constitution, was not followed” and the individual’s rights and liberties were violated.  A hearing is scheduled, the accusers may be cross examined, and witnesses called to support or attack different aspects of the reasons for and procedures used in obtaining the search warrant and any evidence.  If the Judge does not find the evidence was obtained illegally, the defendant may argue or plead his case to a jury as the final arbiter of fact.

If the independent Judge agrees, or a Jury during trial agrees evidence was obtained in violation of law and/or the Constitution, then all of the evidence determined to be obtained illegally, and any evidence obtained as a result of the illegally gotten evidence, is thrown out, disregarded, during the trial of the accused.  This is the concept of “fruit of the poisonous tree”.

All of this procedure, the checks and balances, is possible because the affidavit for search warrant, the signed warrant, and the search warrant inventory return, are public records and discoverable to the public.  If these 3 items remain secret forever, then there can be no review of specific law enforcement agency and individual actions.

If there are no consequences for law enforcement officers and agencies “breaking the law”, then there is no incentive encouraging agencies and officers to follow the law and Constitution.

If:  secret law enforcement officers, swearing to secret facts which are never reviewed by an independent judge or jury, with a secret judge, with secret evidence taken, with secret defendants arrested …

Then:  how can anyone, the world, ever know if “the law”, the Constitution, is in truth and fact, being followed?

Answer:  No independent American, Judge, agency, or jury can possibly verify and/or confirm a secret.

The Washington Post reports, the chief Judge of the Federal Intelligence Surveillance Court admits publicly the role and limitations of the Federal courts in the FISC court:

“The FISC is forced to rely upon the accuracy of the information that is provided to the Court,” its chief, U.S. District Judge Reggie B. Walton, said in a written statement to The Washington Post. “The FISC does not have the capacity to investigate issues of noncompliance, and in that respect the FISC is in the same position as any other court when it comes to enforcing [government] compliance with its orders.”

Walton’s comments came in response to internal government records obtained by The Post showing that National Security Agency staff members in Washington overstepped their authority on spy programs thousands of times per year.

The records also show that the number of violations has been on the rise.

The court’s description of its practical limitations contrasts with repeated assurances from the Obama administration and intelligence agency leaders that the court provides central checks and balances on the government’s broad spying efforts. They have said that Americans should feel comfortable that the secret intelligence court provides robust oversight of government surveillance and protects their privacy from rogue intrusions.

President Obama and other government leaders have emphasized the court’s oversight role in the wake of revelations this year that the government is vacuuming up “metadata” on Americans’ telephone and Internet communications.

“We also have federal judges that we’ve put in place who are not subject to political pressure,” Obama said at a news conference in June. “They’ve got lifetime tenure as federal judges, and they’re empowered to look over our shoulder at the executive branch to make sure that these programs aren’t being abused.”

Privacy advocates and others in government have voiced concerns about the ability of overseers to police secret programs of immense legal and technological complexity. Several members of the House and Senate intelligence committees told The Post last week that they face numerous obstacles and constraints in questioning spy agency officials about their work.

In 2009, for example, a Justice Department review uncovered a major operational glitch that had led to a series of significant violations of the court’s order and notified the court, according to records that were declassified July 31 by the Office of the Director of National Intelligence.

In September 2009, NSA Director Keith B. Alexander made a presentation to the FISA court about the agency’s effort to remedy the problem.“FISA Court placed several restrictions on aspects of the business records collection program until the compliance processes were improved to its satisfaction,” the memo stated.

The only known details of a 2011 ruling that found the NSA was using illegal methods to collect and handle the communications of American citizens.

How NSA analysts explain their targeting decisions without giving “extraneous information” to overseers.

Agency also has overstepped legal authority since Congress gave it broad new power in 2008.

Some lawmakers called Friday for greater transparency in the surveillance operations of the National Security Agency, while U.S. officials stressed that any mistakes committed by the agency were not intentional. The contrasting reactions came after The Washington Post reported that the NSA violated rules or overstepped its legal authority ….

The public summaries of the violations do not say how long the problem went undetected and unreported to the court, or what information was improperly gathered by the agency’s automated collection systems.“The problems generally involved the implementation of highly sophisticated technology in a complex and ever-changing communications environment which, in some instances, results in the automated tools operating in a manner that was not completely consistent with the specific terms of the Court’s orders,” according to unredacted portions of a December 2009 memo provided to the Senate and House intelligence committees.Two people familiar with the 2009 flaw said that the agency was collecting more “fields” of information from the customer records of telephone companies than the court had approved. The NSA declined to answer questions about the event.One senior intelligence official, who was authorized by the White House to speak on the condition of anonymity, described the 2009 incident as a “major event” that prompted the agency to dramatically increase its compliance staff.“We uncovered some disconnects between us and our overseers, disconnects between what we had put in documentation, the way we had described things in documentation,” the official said.Although the violation was unintentional, the official said, “it wasn’t always the easiest of discussions” with the court.The agency paused, “got ourselves with our overseers back into fair territory,” and has since made “substantial improvement” in compliance, the official said.

Privacy advocates say they fear that some violations are never reported to the court.

In January 2008, the NSA appeared to have mistakenly collected data on numerous phone calls from the Washington area code 202, thinking they were foreign phone calls from Egypt, whose country code is 20. According to a 2013 “quality assurance” review of the incident, a communications switch misread the coding of the calls and presumed they were international. The NSA has broad authority that is not subject to the FISA court to collect and monitor foreign communications under certain circumstances.

The description of the 2008 problem suggests that the inadvertent collection of U.S. phone calls was not reported to the FISA court.

“However, the issue pertained to Metadata ONLY so there were no defects to report,” the review stated.

Under FISA rules, the government is required to immediately notify the court if it believes it has violated any of its orders on surveillance.

The government does not typically provide the court with case-specific detail about individual compliance cases, such as the names of people it later learned it was improperly searching in its massive phone or e-mail databases, according to the two people familiar with the court’s work.

In contrast to the dozens of staff available to Congress’s intelligence and judiciary committees, the FISA court has five lawyers to review compliance violation reports.

A staff lawyer can elevate a concern about a significant compliance issue to a judge on the court, according to a letter Walton recently sent to the Senate describing the court’s role.

The court can always demand and obtain more details about cases, but it is unclear how often that occurs. In the past, while grappling with rules for implementing the surveillance programs, judges on the court have requested a visit to NSA headquarters to inspect the operations, the officials said.

…

Barton Gellman, Peter Wallsten and Alice Crites contributed to this report.