Is there a way to exclude a Maven dependency globally?

Does this help? http://jlorenzen.blogspot.com/2009/06/maven-global-excludes.html

"Assuming I want to exclude avalon-framework from my WAR, I would add the following to my projects POM with a scope of provided. This works across all transitive dependencies and allows you to specify it once.

<dependencies>
  <dependency>
      <artifactId>avalon-framework</artifactId>
      <groupId>avalon-framework</groupId>
      <version>4.1.3</version>
      <scope>provided</scope>
  </dependency>
</dependencies>

This even works when specifying it in the parent POM, which would prevent projects from having to declare this in all child POMs."

To expand on dnault's comment:

One can use the Maven Enforcer plugin's Banned Dependencies rule to ensure dependencies are excluded. One still has to exclude them manually, but the build will fail if anyone adds the dependency elsewhere by mistake.

<dependencies>
  <dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-jmx</artifactId>
    <version>3.3.2.GA</version>
    <exclusions>
      <exclusion>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
      </exclusion>
    </exclusions>
  </dependency>
</dependencies>

<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-enforcer-plugin</artifactId>
    <version>1.4.1</version>
    <executions>
      <execution>
        <goals>
          <goal>enforce</goal>
        </goals>
        <configuration>
          <rules>
            <bannedDependencies>
              <excludes>
                <exclude>org.slf4j:slf4j-api</exclude>
              </excludes>
            </bannedDependencies>
          </rules>
        </configuration>
      </execution>
    </executions>
  </plugin>
</plugins>

Also there is an open feature request: MNG-1977 Global dependency exclusions

I created an empty jar and created this dependency:

<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <scope>system</scope>
    <systemPath>${basedir}/src/lib/empty.jar</systemPath>
    <version>0</version>
</dependency>

It is not perfect because from now on you have an empty jar in your compile/test path. But that is just cosmetic.

As a reminder, here is the answer from Maven official documentation:

Why exclusions are made on a per-dependency basis, rather than at the POM level This is mainly done to be sure the dependency graph is predictable, and to keep inheritance effects from excluding a dependency that should not be excluded. If you get to the method of last resort and have to put in an exclusion, you should be absolutely certain which of your dependencies is bringing in that unwanted transitive dependency.

If one wants to make a build more robust, a version range can be used. This would ensure that no newer version of the dependency can interfere with the project.

<dependency>
   <groupId>org.slf4j</groupId>
   <artifactId>slf4j-api</artifactId>
   <version>[1.4.2,)</version>
   <scope>provided</scope>
</dependency>

Any slf4j-api version >= 1.4.2 will be considered as offered (provided) at runtime, either from a configured classpath or a container.

References

Maven version range

Optional Dependencies and Dependency Exclusions