In an escalation of Martin O’Malley’s war on the Democratic National Committee over the party’s primary debate process, an attorney for his presidential campaign is saying the DNC’s plan may run afoul of federal election rules.

In a memo shared with msnbc, O’Malley attorney Joe Sandler, who formerly served as the DNC’s general counsel, calls the DNC’s debate plan “entirely unprecedented” and “legally problematic.”

The DNC last week announced the schedule for its six presidential primary debates, including four before the Iowa Caucuses and two afterwards. O’Malley and fellow candidate Bernie Sanders came out against the schedule, demanding, as they have for months, more chances to face off on stage against front-runner Hillary Clinton.

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Of particular concern to O’Malley is the DNC’s exclusivity requirement, which would punish candidates and debate sponsors who participate in unsanctioned debates by barring them from participating in remaining official events. The DNC’s goal was to limit the unwieldy sprawl of the last Democratic primary in 2008, when the number of debates mushroomed to about two dozen.

But O’Malley’s attorney says that exclusivity clause is “legally unenforceable.”

“Under Federal Election Commission rules, the format and structure of each debate must be controlled exclusively by the debate sponsor, not by any party or candidate committee,” Sandler wrote in the memo.

The six debates are sponsored by 10 media outlets and one non-profit organization. “Legally the DNC cannot dictate the format or structure of any debate sponsored by a media outlet or 501(c)(3) organization – including the criteria for participation,” Sandler added. “It would be legally problematic if any of the sponsors of the sanctioned debates has actually agreed to the ‘exclusivity’ requirement. And in any event, it is highly unlikely that any of those sponsors of the sanctioned debates would ultimately be willing to enforce that ‘exclusivity’ requirement.”

In response, the Democratic National Committee said it did not set the rules of inclusion on its own, but rather worked in tandem with debate sponsors to set a unified standard. “We agreed with the networks on a standardized criteria across all debates,” said DNC spokesperson Miryam Lipper.

“Shame on us as a party if the DNC tries to limit debate.” Martin O'Malley

Sandler — O’Malley’s lawyer who served as general counsel to the DNC from 1993 through 2008, first in-house and then through his law firm — also says the party has never used an exclusivity clause in the past.

“Although the DNC announced a schedule of sanctioned debates both in 2004 and 2008, it has never before attempted to require debate sponsors to exclude any recognized candidate as punishment for participating in non-sanctioned debates,” wrote Sandler. All major candidates in 2008, including Barack Obama and Hillary Clinton, participated in unsanctioned debates, he said.

After the DNC announced the schedule of it debates last week, O’Malley launched a crusade against the party to increase the number of debates. “Shame on us as a party if the DNC tries to limit debate,” O’Malley said on msnbc Monday. “I believe we need more debates, not fewer debates. And I think it’s outrageous, actually, that the DNC would try to make this process decidedly undemocratic.”

While campaigning in New Hampshire Monday, Clinton was asked if she would prefer more debates. “I’m just going to show up, and when I’m told to show up, I’ll be there and looking forward to it,” she demurred.

As the Republicans recently experienced, the rule for inclusion in debates is often a heated subject in presidential primaries. In 2007, a hot mic caught Clinton and then-rival candidate John Edwards discussing the idea of a debate between a smaller number of candidates.

“We are thrilled the candidates are so eager to participate in our debates. We believe that six debates will give plenty of opportunity for the candidates to be seen side-by-side,” said DNC National Press Secretary Holly Shulman. “I’m sure there will be lots of other forums for the candidates to make their case to voters, and that they will make the most out of every opportunity.”