HHS regulations stipulate that there are only limited circumstances in which a grant can be canceled: for cause, such as when the grant fails to comply with the terms and conditions of the award, or with the consent of the grantee.
Source: wiktionary
The cancellations, which claimed that the more than 350 already-distributed grants “no longer effectuates the program goals or agency priorities,” sent shockwaves through grantee organizations. […] When news of the cuts first surfaced Tuesday, dozens of grantees gathered on a videoconference to discuss their options, including whether to take legal action.
Source: wiktionary