It's impossible for Trump to 'obstruct justice,' his lawyer says Trump's lawyer John Dowd outlines new defense in Russia probe.

 -- President Donald Trump's personal lawyer today outlined a new pre-emptive legal defense in the ongoing Russia probes: The president cannot be guilty of obstruction of justice in his role.

A sitting president cannot obstruct justice, Trump lawyer John Dowd told ABC News in a statement today, citing Article II of the Constitution.

The "president cannot obstruct justice because he is the chief law enforcement officer under Art II and has every right to express his view of any case," Dowd added.

The outline, first reported by Axios this morning and later confirmed by ABC News, comes two days after Trump tweeted that he had fired his former national security adviser, retired Lt. Gen. Michael Flynn, because "he lied to the Vice President and the FBI."

Trump's tweet sparked renewed talk of possible evidence of obstruction of justice because his tweet seemed to acknowledge that he knew Flynn had lied to FBI investigators before firing him in February.

Dowd confirmed to ABC News he drafted Trump's social media post and sent it to Trump's social media director, Dan Scavino.

Former FBI Director James Comey testified in June before Congress that Trump asked him to "let this go" — drop the FBI's investigation of Flynn in connection with his false statements about his conversations with Russia's then-Ambassador Sergey Kislyak in December.

The special counsel's office announced Friday that Flynn pleaded guilty to one count of lying to the FBI about his negotiations with Kislyak before Trump assumed office.

Special counsel Robert Mueller and his team have been investigating Russian meddling in the 2016 presidential election and possible ties between Russia and Trump campaign associates since May.