If a participant is enrolled in Cobra (not through a ARRA subsidy) and they have other coverage available to them, either through their employer or their spouse's employer can the cobra employer drop them from coverage? How do you monitor whether or not your cobra particpants have other coverage?

COBRA can be continued if the former employee is eligible for other group coverage. The former employer cannot drop them from coverage due.

54.4980B-7 Question 2

Q-2: When may a plan terminate a qualified beneficiary's COBRA
continuation coverage due to coverage under another group health plan?
A-2: (a) If a qualified beneficiary first becomes covered under
another group health plan (including for this purpose any group health
plan of a governmental employer or employee organization) after the date
on which COBRA continuation coverage is elected for the qualified
beneficiary and the other coverage satisfies the requirements of
paragraphs (b), (c), and (d) of this Q&A-2, then the plan may terminate
the qualified beneficiary's COBRA continuation coverage upon the date on
which the qualified beneficiary first becomes covered under the other
group health plan (even if the other coverage is less valuable to the
qualified beneficiary). By contrast, if a qualified beneficiary first
becomes covered under another group health plan on or before the date on
which COBRA continuation coverage is elected, then the other coverage
cannot be a basis for terminating the qualified beneficiary's COBRA
continuation coverage.
(b) The requirement of this paragraph (b) is satisfied if the
qualified beneficiary is actually covered, rather than merely eligible
to be covered, under the other group health plan.
(c) The requirement of this paragraph (c) is satisfied if the other
group health plan is a plan that is not maintained by the employer or
employee organization that maintains the plan under which COBRA
continuation coverage must otherwise be made available.
(d) The requirement of this paragraph (d) is satisfied if the other
group health plan does not contain any exclusion or limitation with
respect to any preexisting condition of the qualified beneficiary (other
than such an exclusion or limitation that does not apply to, or is
satisfied by, the qualified beneficiary by reason of the provisions in
section 9801 (relating to limitations on preexisting condition exclusion
periods in group health plans)).
(e) The rules of this Q&A-2 are illustrated by the following
examples:

Example 1. (i) Employer X maintains a group health plan subject to
COBRA. C is an employee covered under the plan. C is also covered under
a group health plan maintained by Employer Y, the employer of C 's
spouse. C terminates employment (for reasons other than gross
misconduct), and the termination of employment causes C to lose coverage
under X 's plan (and, thus, is a qualifying event). C elects to receive
COBRA continuation coverage under X 's plan.
(ii) Under these facts, X 's plan cannot terminate C 's COBRA
continuation coverage on the basis of C 's coverage under Y 's plan.
Example 2. (i) Employer W maintains a group health plan subject to
COBRA. D is an employee covered under the plan. D terminates employment
(for reasons other than gross misconduct), and the termination of
employment causes D to lose coverage under W 's plan (and, thus, is a
qualifying event). D elects to receive COBRA continuation coverage under
W 's plan. Later D becomes employed by Employer V and is covered under V
's group health plan. D 's coverage under V 's plan is not subject to
any exclusion or limitation with respect to any preexisting condition of
D.
(ii) Under these facts, W can terminate D 's COBRA continuation
coverage on the date D becomes covered under V 's plan.
Example 3. (i) The facts are the same as in Example 2, except that D
becomes employed by V and becomes covered under V 's group health plan
before D elects COBRA continuation coverage under W 's plan.
(ii) Because the termination of employment is a qualifying event, D
must be offered COBRA continuation coverage under W 's plan, and W is
not permitted to terminate D 's COBRA continuation coverage on account
of D 's coverage under V 's plan because D first became covered under V
's plan before COBRA continuation coverage was elected for D.