Rule resolution processing is halted (with no rule found) when it encounters blocked rules. The rule form colors change from greens to grays for blocked rules.
Blocked and blocked-by-another
A rule instance is blocked-by-another if its Availability value is set to Available but a higher-numbered version of this rule (same name or key, same ruleset) has the Availability set to Blocked.
Available rules with that name or key and a different ruleset may be blocked-by-another as well, if their ruleset version is appears beneath the ruleset version of the Blocked rule on the user's ruleset list.
When rule resolution selects a rule that is blocked, that rule and all others (same name or key, any ruleset) are not executable.
To make a rule available "above" a blocked rule (that belongs to a secure ruleset version), choose a higher version number or a ruleset that appears higher on your (and other users') ruleset list.
If a rule has Availability set to Blocked but also has a non-blank Circumstance Property, the blocking affect applies both to that rule and the base or underlying rule that has no Circumstance property. A rule resolution search that meets the Circumstance Property value stops (with no rule found). The Availability setting in the underlying rule is not relevant.
However, the converse does not hold. If the rule with a Circumstance Property has Availability set to Available, and the base rule has Availability set to Blocked, a rule request matching the circumstance property and value is successful at finding and using the circumstance-qualified rule.
Blocked rules included in ZIP archives
When you create a ZIP archive containing a ruleset version, any blocked rules associated with that ruleset Version are included in the archive (and remain blocked when uploaded into on a destination system).
On a destination system, a blocked rule can in some cases block a different set of other rules than it blocked on the source system.
Blocked rules and skimming
When skimming to a new minor or major ruleset Version, Blocked rules are always copied since their purpose is to block all similar rules regardless of ruleset name. Blocked rules can be used, for example, to block another rule which belongs to a ruleset name in an underlying Application layer that will be untouched by the skim process.