Since we are dealing with software used to spy on Americans in the U.S. and abroad, the constitutional right being transgressed is the right to privacy.

This is the ancient natural right to be left alone, which the Supreme Court took 175 years to recognize as being protected by the Fourth Amendment. Since that recognition in 1965, however, notwithstanding near universal judicial acceptance of the constitutional protection of the right, the executive branch of the government has persistently negated it.

Here is the backstory.

The Fourth Amendment, which requires judicially issued search warrants for all searches and seizures, protects the contents of devices that store data. Thus, the owners of mobile devices and desktop computers have a privacy right in the data they have stored there. Even a narrow interpretation of the amendment, which guarantees privacy in "persons, houses, papers, and effects," must acknowledge that a computer chip is an "effect" and thus its owner enjoys this protection.