SAN FRANCISCO — Deals are coming back — and so are the trustbusters. Lawyers are expecting to see more transactions in 2010 and are watching to see what the reinvigorated antitrust regulators in Washington, D.C., have up their sleeves.

Deals all but died in late 2008 and early 2009, but there was a rally in the second half of the year as the economy improved. It was kicked off by a deal that was emblematic of the shift in the market and antitrust regulation: Oracle Corp.’s $7.38 billion acquisition of Silicon Valley icon Sun Microsystems Inc. in late April.