WASHINGTON (CN) – Fighting to suppress evidence obtained with a search warrant, former Trump campaign chair Paul Manafort argued in a court filing Friday that the FBI entered his Virginia storage unit a day before the search with improper authorization.

Manafort’s arguments comes in response to an April 23 brief by the government where it said an employee of a Manafort business gave agents written consent to enter the unit with his key.

But Manafort says this argument is legally “incorrect because it conflates the right to enter the storage unit with the informant’s physical capability to do so.” (Emphasis in original.)

“The former DMP employee’s possession of a key to the storage unit gave him only the physical ability to enter the storage unit (unauthorized) without Mr. Manafort’s permission — just as a hotel manager’s access key would give him/her the ability to enter a guest’s room without permission,” the reply brief states, using an abbreviation for Davis Manafort Partners Inc.

Manafort contends that the results of this May 26, 2017, entry led federal authorities to quickly obtain a warrant that they used the next day to seize most of the storage unit’s contents.

Andrew Weissmann with the Office of Special Counsel claimed last week, however, that the employee was more than a key holder, having been listed as the unit’s occupant on the lease and having “personally moved the contents of the unit into the unit.”

A copy of the storage unit lease filed on April 6 by Manafort’s defense attorney, Kevin Downing, names Alexander Trusko as the “occupant” of the storage unit.

In the latest brief meanwhile Downing says the agent should have inquired why Trusko, and not Manafort, was named on the lease, pointing to the D.C. Circuit’s disapproval of failure to ascertain such information in United States v. Whitfield.

“Critically, Whitfield held that even if the third party’s ability (or legal right) to access the property established the joint access or control element of common authority, it did not establish the mutual use element,” the brief says.

Manafort contends that Trusko specifically told the FBI “that he was permitted to enter the premises only at Mr. Manafort’s direction.” (Emphasis original.)

He says the special counsel’s team has presented no evidence that the agent reasonably investigated Trusko’s authority to unlock the storage unit and conduct an initial search without a warrant.

The FBI agent should have asked Trusko whether he could enter the unit without Manafort’s permission, and whether he was allowed to store his own belongings there to establish that he had mutual use of the unit, according to the brief.

For Manafort, the FBI agent’s failure to ask appropriate follow-up questions and include that information in the search warrant application “speaks volumes.”

The searches were conducted as part of the charges special counsel Robert Mueller brought against Manafort for work he did on behalf of a pro-Russian political party in Ukraine and former Ukrainian president Viktor Yanukovych.

The Office of Special Counsel did not immediately respond to a request for comment on the ruling. Attorney Downing likewise did not immediately return an email seeking comment.