Glamorgan cleared over declaration after Derby protest
The Welsh county declared their first innings on 103-4, 102 runs behind.
Derbyshire claimed they had been unfairly deprived of the chance to earn bowling bonus points.
But a statement from the ECB's Discipline Commission said: "Counties must have a wide discretion in deciding the best way to approach a game."
Glamorgan's declaration during the game in Cardiff in May, which was badly disrupted by rain, was made hoping to profit from good bowling conditions and to improve a poor over-rate from Derbyshire's first innings.
Deputy chairman of the ECB's Discipline Commission, Mike Smith, considered the complaint and decided not to take any further action.
There was no criticism of Derbyshire for making the protest and the commission added that: "Any complaint under Playing Condition 14 will be carefully considered on its individual merits and the particular circumstances of the game."
Law 14 covers extraordinary declarations and "is usually a declaration aimed primarily at denying the bowling side the opportunity to acquire further bonus points in that innings, but without enhancing the batting side's prospects of winning or saving the match".
Play did not resume on the evening of Glamorgan's declaration because of further weather problems, with Derbyshire then batting out time on the final day.
Glamorgan were able to improve their over-rate and avoid being docked points.