California state Sen. Leland Yee appeared in federal court on Monday morning, stemming from a shocking arrest last week where FBI agents charged him with seven felonies related to firearms trafficking and promising political favors.

The hearing before U.S. District Court Magistrate Judge Nathanael Cousins was mostly uneventful. Attorneys discussed the terms of Yee's $500,000 unsecured bond. Yee didn't say much during the hearing, but smiled before heading off to the federal building, looking more well rested than he did when he was arrested by FBI agents on Wednesday.

Before hopping into a car, Yee casually waved to an NBC Bay Area reporter and said in a businesslike tone: "I'll see you in court." His next court apperance is scheduled for April 8.

Previously, his attorney, Paul DeMeester told the media that Yee intends to plead not guilty to the charges.

Sen. Leland Yee's attorney, Paul DeMeester, speaking with the media after court. March 31, 2014.

Outside court, DeMeester noted to reporters that this investigation has been going on since 2011 and questioned aloud "what took three years?" He criticized the FBI agents for "pushing this idea of the arms dealing," noting that the firearm trafficking charges came late in the investigation.

NBC Bay Area broke news of Yee's arrest.

On Friday, Yee was suspended by the state Legislature; the day before, he withdrew from his bid for Secretary of State.

The 137-page federal affidavit (PDF) charges the San Francisco Democrat - a longtime vocal advocate of gun control - with conspiring to commit wire fraud and traffic firearms, and that he, along with political consultant Keith Jackson, allegedly defrauded citizens of "honest services."

Yee and 25 others, including Raymond "Shrimp Boy" Chow - Chinatown gang leader known as a "Dragonhead -" were caught up in a multi-year undercover FBI operation. Chow, dressed in a yellow Alameda County jail jumpsuit, also appeared in court on Monday to be appointed an attorney. Finding him one has been a challenge because the public defender's office has already defended him during previous criminal charges.

Jackson was told to return to court on Tuesday.

Despite the evidence against Yee, which to many, appeard overwhelming, some legal experts said those charges could be hard to prove.

Legal Analyst Dean Johnson said it is not illegal for a person to give money to a politician’s campaign, expecting to influence that politician. It is also not illegal for a politician to take into account the wishes of contributors when making decisions.

But the illegal part is if there is a quid pro-quo or a tit -or-tat, a blatant exchange of money for political favors. Johnson said proving that can be tricky.

"Legally, this case is wide open," Johnson said. "These are kinds of cases that defense attorneys love because so much is open to interpretation, and everything turns on what was going on in Sen. Yee’s head. What was his intent?"

Johnson said the strength of the prosecutors case will also depend on how much video and audio evidence there is, and he said he assumes there is such evidence.

Johnson also said Yee’s attorney will likely argue the FBI entrapped Yee by setting up such an elaborate sting, with made up scenarios and crimes that, in the end, never took place.

NBC Bay Area's Monte Francis and Vince Cestone contributed to this report.