Saying it had the right to block "controversial or unsavory" text messages, Verizon Wireless has rejected a request from Naral Pro-Choice America, the abortion rights group, to make Verizon's mobile network available for a text-message program.
The other leading wireless carriers have accepted the program, which allows people to sign up for text messages from Naral by sending a message to a five-digit number known as a short code.
Text messaging is a growing political tool in the United States and a dominant one abroad, and such sign-up programs are used by many political candidates and advocacy groups to send updates to supporters.
But legal experts said private companies like Verizon probably have the legal right to decide which messages to carry. The laws that forbid common carriers from interfering with voice transmissions on ordinary phone lines do not apply to text messages.
The dispute over the Naral messages is a skirmish in the larger battle over the question of "net neutrality" - whether carriers or Internet service providers should have a voice in the content they provide to customers.
"This is right at the heart of the problem," said Susan Crawford, a visiting professor at the University of Michigan law school, referring to the treatment of text messages. "The fact that wireless companies can choose to discriminate is very troubling."
In turning down the program, Verizon, one of the nation's two largest wireless carriers, told Naral that it "does not accept issue-oriented (abortion, war, etc.) programs - only basic, general politician-related campaigns (Mitt Romney, Hillary Clinton, etc.)." Naral provided copies of its communications with Verizon to The New York Times.
Nancy Keenan, Naral's president, said Verizon's decision interfered with political speech and advocacy.
"No company should be allowed to censor the message we want to send to people who have asked us to send it to them," Ms. Keenan said. "Regardless of people's political views, Verizon customers should decide what action to take on their phones. Why does Verizon get to make that choice for them?"
A spokesman for Verizon said the decision turned on the subject matter of the messages and not on Naral's position on abortion. "Our internal policy is in fact neutral on the position," the spokesman, Jeffrey Nelson, said. "It is the topic itself" - abortion - "that has been on our list."
Mr. Nelson suggested that Verizon may be rethinking its position. "As text messaging and multimedia services become more and more mainstream," he said, "we are continuing to review our content standards." The review will be made, he said, "with an eye toward making more information available across ideological and political views."
Naral provided an example of a recent text message that it had sent to supporters: "End Bush's global gag rule against birth control for world's poorest women! Call Congress. (202) 224-3121. Thnx! Naral Text4Choice."...
Timothy Wu, a law professor at Columbia, said it was possible to find analogies to Verizon's decision abroad. "Another entity that controls mass text messages is the Chinese government," Professor Wu said.
This is a direct attack on the right of assembly and the right to free speech. I know of several companies that sell mass texting services, and none of them will go on the record about carriers because they are afraid of them. And keep in mind, these telecom companies want retroactive immunity for breaking the law and spying on Americans.
