The following works in 1.5, but not the latest 1.6 builds:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ActionTest {
    public static void main(String[] args) {
        Action action = new FooAction();
        JToolBar toolBar = new JToolBar();
        JButton toolBarButton = toolBar.add(action);
        JButton button = new JButton(action);

        // action.setEnabled(false);
        action.putValue("enabled", Boolean.FALSE);
        if (toolBarButton.isEnabled()) {
            System.out.println("toolbar button should not be enabled");
        }
        if (button.isEnabled()) {
            System.out.println("button should not be enabled");
        }
    }

    private static class FooAction extends AbstractAction {
        public void actionPerformed(ActionEvent e) {
        }
    }
}