There is a federal law saying that lobbyists need to be granted a waiver to work in the administration. This is overseen by the Office of Government Ethics. Historically, for both Democrat and Republican administrations, the White House has complied with providing these waivers.
The Trump Administration has not provided these waivers. Walter Shaub, the director of the OGE, has set a deadline of June 1 to provide these documents. The White House Council has provided instructions to employees to not provide this documentation, claiming providing them would be an undue administrative burden. This raises the question of why it would be an undue burden: due to the number of people provided waivers or the extent of the waivers granted.
Editorializing a bit, it is both heartening that the head of the office for Ethics is willing to proverbially "walk the talk" by putting his own position at risk to do the right thing, as well as depressing that such behavior is the laudable exception rather than the accepted norm.