They cannot take the loan unless it is for coronavirus related hardship. If an employee was terminated before the date of the enactment of the CARES Act, they would not qualify for the distribution unless they are experiencing financial hardship as a result of the virus. So, if they were laid off before 3/27/2020 because of the virus, they could apply for the loan. For employees terminated before the virus crisis, they would not qualify for the loan.
All "rules" of distributions and loans are not applicable to this distribution, per the CARES Act. "(B) TREATMENT OF PLAN DISTRIBUTIONS.—If a distribution to an individual would (without regard to subparagraph (A)) be a coronavirus-related distribution, a plan shall not be treated as violating any requirement of the Internal Revenue Code of 1986 merely because the plan treats such distribution as a coronavirus-related distribution, unless the aggregate amount of such distributions from all plans maintained by the employer (and any member of any controlled group which includes the employer) to such individual exceeds $100,000."