"Verizon Wireless' decision to block legal content from users of its service raised serious questions about whether it was adhering to basic network neutrality principles," Rep. Edward Markey, D-Mass., chairman of the House Energy and Commerce Telecommunications and the Internet Subcommittee, said in a statement.

Markey has championed legislation designed to mandate non-discrimination of content, but controversy over the issue has prevented his measure and similar bills from advancing this year.

While pleased about the reversal, Markey added, "I urge Verizon and other wireless carriers to ensure that their company policies do not interfere with the delivery of any lawful content, nor discriminate on the basis of who the sender of such messages may be."

House Energy and Commerce Chairman John Dingell, D-Mich., said in a statement that Verizon's actions "raise troubling questions about a network operator's ability to determine what its customers receive and from whom." He urged Verizon "to decisively state that it will no longer discriminate against any legal content its customers request from any organization."

The company did not respond to a request for comment on Dingell's concerns. But on Thursday, Verizon Wireless pledged to "continue to protect the ability to communicate broadly through our messaging." It said the decision to bar the text-messaging was "incorrect" and that it has addressed the processes that prompted this "isolated incident."

The American Civil Liberties Union and media advocacy groups, including Free Press and Public Knowledge, pointed to the carrier's actions as an argument for network neutrality safeguards.

"This is just yet another example of why we can't trust the biggest phone and cable companies to be gatekeepers of the entire Internet," Free Press spokesman Craig Aaron said in an interview. "Every time one of these instances happens, they claim it was a glitch. For those of us whose glitches might not be covered in The New York Times, we need a little more assurance."