Remember, he was Sec State at the time, and thought that he was next in the line of succession after Nixon and Agnew resigned. Under the US Constitution, the Speaker of the House--not Haig--was "in charge."
That incident was during Reagan's presidency on the day he was shot. If I remember correctly, he meant only that he was in charge of the information gathering and press briefing at the WH, but the press hated him as much as they hate W, and blew it out of proportion.