This action is due to misuse of ARIN’s Whois services: specifically, organizations that routinely misuse the Whois data risk losing access to the information. 

As I noted elsewhere, it is possible for the suspension of access to Whois to be technically circumvented, but ARIN still has to take abuse of the data seriously because our customers make their contact data available specifically for facilitating network operations, and this includes terminating or suspending access to the Whois service for those who chronically fail to comply with the terms of use, such as those who repeatedly violate the prohibition on marketing & solicitation using ARIN Whois data. 

It is also possible that such misuse of ARIN Whois is a violation of ARIN’s registration services agreement (which provides for more significant recourse such as resource revocation), but ARIN is simply suspending access to the Whois service as that action directly corresponds to (and helps mitigate) the specific terms of use violation.