The filing states an intention to explore a bid but does not give terms of any potential deal.
The news comes the same day BlackBerry announced it was shutting its Nova Scotia office, entailing the loss of 350 jobs.
Lazaridis was rumoured to be talking to private equity firms a month ago, seeking support to take BlackBerry private, but his SEC filing specifies he is working only with Fregin.
Fregin and Lazaridis formed Research in Motion, the precursor to BlackBerry, in 1984.
Lazaridis is former president, co-CEO and co-chair of BlackBerry. He and Fregin together own about 16 per cent of the company
Fregin was vice-president of operations and designed the first circuit boards that were used in early versions of the company's wireless technology, but resigned from the company in 2007. He is now management partner of Quantum Valley Investments.
Fairfax Financial Holdings Ltd. has made an offer to buy BlackBerry for $4.7 billion, although the deal is currently tentative.
BlackBerry is known to be soliciting rival bids in the meantime, with companies such as SAP AG, Cisco Systems and Samsung Electronics reported to have approached its advisers.
However, the tech titans are likely interested only in pieces of the company, Bloomberg reported, adding that BlackBerry company management is becoming more open to a breakup of the company.
The federal government’s move to quash a deal by Egyptian firm Accelero to take over national telecom provider MTS Allstream may have bidders thinking twice about investing in Canada. The government nixed the deal over "national security concerns" but gave little further explanation.
Treasury Board President Tony Clement said Tuesday that national security would play a role in assessing offers for BlackBerry as well.