Reemployment after Retirement

[Guest ERISAQuestioner]

Does anybody know the IRC Section, the reg., the ruling, or letter, that makes this requirement:

"Internal Revenue Service (IRS) guidelines prohibit distributions from a qualified pension plan to participants who are actively employed in either a full-time or part-time position with an employer covered by the plan. This prohibition extends to participants under the age of 59 ½ years who are re-employed after retirement without a bona fide break in service. The IRS may impose a 10% penalty on your retirement benefit if you violate the prohibition.

Consequently, you must be removed from the County payroll for at least 30 days before being reemployed by the County. Also, your decision to retire must not be conditioned upon an offer of re-employment."

This requirement is in every plan but I can't find the source which requires it. Anybody know offhand or have any suggestions? And, may employees over the age of 59 1/2 be reemployed without any break in service--any prohibition on that?