Is that true? Regulatory bodies get their authority from congressional legislation. Can a president unilaterally tell the bureaucracy to stop doing what they are mandated to do by law?
In the general case, though, a lot of legislation gives the executive wide discretion as to the details of regulations, and so the president can direct his subordinates to change regulations however he wants, within what the law allows.
E.g. with a budget example the Congress might want to subsidise cantaloupe farms, and budget $100,000,000 for cantaloupe farmers, to be allocated 'as the Secretary of Agriculture may direct.' The president would be within his rights to order the Secretary of Agriculture to only allocate that money to cantaloupe farmers with a total net worth of under $1,000,000, or to give no more than $100,000 to any particular cantaloupe farmer, or (possibly — this one's a stretch) to prioritise farmers of the famed Golden Lucy cantaloupe before all others. But he can't direct that the money be spent on rutabaga farmers.
Similarly, if the Congress writes a law which gives the pertinent executive department some latitude, the President may order that department to exercise that latitude however he likes.
He can certainly try: http://www.npr.org/sections/thetwo-way/2014/11/20/365519963/...
In the general case, though, a lot of legislation gives the executive wide discretion as to the details of regulations, and so the president can direct his subordinates to change regulations however he wants, within what the law allows.
E.g. with a budget example the Congress might want to subsidise cantaloupe farms, and budget $100,000,000 for cantaloupe farmers, to be allocated 'as the Secretary of Agriculture may direct.' The president would be within his rights to order the Secretary of Agriculture to only allocate that money to cantaloupe farmers with a total net worth of under $1,000,000, or to give no more than $100,000 to any particular cantaloupe farmer, or (possibly — this one's a stretch) to prioritise farmers of the famed Golden Lucy cantaloupe before all others. But he can't direct that the money be spent on rutabaga farmers.
Similarly, if the Congress writes a law which gives the pertinent executive department some latitude, the President may order that department to exercise that latitude however he likes.