§ 15-301. When written agreement or other instrument cannot be changed
by oral executory agreement, or discharged or terminated by oral
executory agreement or oral consent or by oral notice. 1. A written
agreement or other written instrument which contains a provision to the
effect that it cannot be changed orally, cannot be changed by an
executory agreement unless such executory agreement is in writing and
signed by the party against whom enforcement of the change is sought or
by his agent.

2. A written agreement or other written instrument which contains a
provision to the effect that it cannot be terminated orally, cannot be
discharged by an executory agreement unless such executory agreement is
in writing and signed by the party against whom enforcement of the
discharge is sought, or by his agent, and cannot be terminated by mutual
consent unless such termination is effected by an executed accord and
satisfaction other than the substitution of one executory contract for
another, or is evidenced by a writing signed by the party against whom
it is sought to enforce the termination, or by his agent.

3. a. A discharge or partial discharge of obligations under a written
agreement or other written instrument is a change of the agreement or
instrument for the purpose of subdivision one of this section and is not
a discharge or termination for the purpose of subdivision two, unless
all executory obligations under the agreement or instrument are
discharged or terminated.

b. A discharge or termination of all executory obligations under a
written agreement or other written instrument is a discharge or
termination for the purpose of subdivision two even though accrued
obligations remaining unperformed at the date of the discharge or
termination are not affected by it.

c. If a written agreement or other written instrument containing a
provision that it cannot be terminated orally also provides for
termination or discharge on notice by one or either party, both
subdivision two and subdivision four of this section apply whether or
not the agreement or other instrument states specifically that the
notice must be in writing.

4. If a written agreement or other written instrument contains a
provision for termination or discharge on written notice by one or
either party, the requirement that such notice be in writing cannot be
waived except by a writing signed by the party against whom enforcement
of the waiver is sought or by his agent.

5. If executed by an agent, any agreement, evidence of termination,
notice of termination or waiver, required by this section to be in
writing, which affects or relates to real property or an interest
therein as defined in section 5-101 in any manner stated in subdivisions
one or two of section 5-703 of this chapter shall be void unless such
agent was thereunto authorized in writing.

6. As used in this section the term "agreement" includes promise and
undertaking.