Suspect Dylann Roof was arrested in February on a felony narcotics charge.
The provision is a part of an annual spy policy bill set to hit the Senate floor in coming days.
"Senior officials make the choice to secretly twist the law," Sen. Ron Wyden (D-Ore.) said.
FBI Director James Comey said the incident does not meet the agency's definition.
The senator called it a "growing threat to Americans’ privacy and safety."
"This is all 50 states and in ways that are very hard to see," said the FBI chief.
Wouldn't it be great if someone in the federal government made a clarion call about the environment...
Currently, a patchwork of state laws faces companies experiencing a data breach.
FBI director wants Congress to revise law to help police.
Officials have no indications that terrorists are seeking to use Ebola as a biologic weapon.
Director James Comey also told "60 Minutes" he appreciates a distrust of government.
The masked "English-speaking individual" appeared in a propaganda film.
Arrests in recent weeks disrupted attacks meant for the holiday weekend, James Comey said.
The FBI has repeatedly warned of recruits leaving to join ISIS or launching attacks at home
Officials warned senators that investigators are being thwarted by encrypted communications.
Director James Comey said the law also gives the FBI important powers.
“I don’t know enough about where the document sits at this point in time,” James Comey said.
OPINION | One person was noticeably absent from the summit: FBI Director James Comey.
The FBI tells local police departments to keep quiet about the technology.
FBI Director Comey revealed a new link between the Sony hackers and North Korea.
Other officials have pointed to China as the largest threat to cybersecurity.
“Justice may be denied because of a locked phone or encrypted device," Comey said.
Portman blasted President Obama’s plan to track U.S. supporters of ISIS as “reckless.”
China is responsible for the most cyberattacks in the United States, Comey said.