Notwithstanding any provision of law to the contrary, but excepting herefrom any meetings of law enforcement officers called pursuant to Section 12524 of the Government Code, when any county officer is called or summoned to attend any meeting or conference by any civil executive officer of the state pursuant to state law, his expenses of attending such meeting or conference may be made charges against the county only when funds for such expenses, exclusive of funds required for mandatory travel expenses, have already been appropriated.