Twitter is contesting a court order requiring it to turn over private data on a user charged with disorderly conduct during the Occupy Wall Street protests in New York last year.
On Monday, the company filed a memorandum in New York's Criminal Court, asserting that users own their content and that it may be unconstitutional to request it without a warrant.
The closely-watched case involves Twitter user Malcolm Harris, who has been charged along with several hundred others for allegedly marching onto the roadway of the Brooklyn Bridge on Oct. 1.
Prosecutors want Harris' tweets between Sept. 15 and Dec. 31, 2011, in order to refute an "anticipated defense" that police led or escorted him onto the bridge's road, according to court documents.
Twitter was served with a subpoena on Jan. 26 ordering it to turn over the information, citing section 2703 of the Stored Communications Act. The Act requires a service provider to disclose certain kinds of electronic communications without a warrant.
Twitter is sticking with Harris. In its memorandum, Twitter said the SCA allows a court to quash an order that causes an "undue burden" on a service provider.
In its arguments, Twitter contended that its terms of service mandate that users retain the rights to their content. It also argued that the SCA has been found to violate the constitutional right against unlawful search and seizure since in some instances it requires the disclosure of information without a search warrant.
The April 20 ruling denying Harris' motion cited a U.S. Supreme Court case in which it was found bank customer records belonged to the bank and were not owned by the customer.
But the court did note that New York courts had not addressed whether a criminal defendant had "standing" to quash a subpoena "issued to a third-party social networking service."
Twitter sought to distinguish itself from banks, arguing that "unlike bank records, the content that Twitter users create and submit to Twitter are clearly a form of electronic communication that, accordingly, implicates First Amendment protections as well as the protections of the SCA."
Ben Lee, Twitter's legal counsel, said in an email statement that the company's terms of service make "absolutely clear" that users own their content. "Our filing with the court reaffirms our steadfast commitment to defending those rights for our users," he said.
The legal fight is being monitored for its potential impacts. Aden Fine, a senior staff attorney with the American Civil Liberties Union, wrote in a blog post that Twitter should be applauded for standing up for Harris since internet companies represent an important line of defense for users' free speech rights.
"This is a big deal," Fine wrote. "Law enforcement agencies -- both the federal government and state and city entities -- are becoming increasingly aggressive in their attempts to obtain information about what people are doing on the Internet."
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