JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/brianreavis/selectize.js/master/dist/js/standalone/selectize.min.js"></script>
<select>
  <option value="1">Value 1</option>
  <option value="2">Value 2</option>
  <option value="3">Value 3</option>
</select>

CSS

.selectize-control.plugin-drag_drop.multi > .selectize-input > div.ui-sortable-placeholder {
  background: #f2f2f2 !important;
  background: rgba(0, 0, 0, 0.06) !important;
  border: 0 none !important;
  visibility: visible !important;
  -webkit-box-shadow: inset 0 0 12px 4px #ffffff;
          box-shadow: inset 0 0 12px 4px #ffffff;
}

.selectize-control.plugin-drag_drop .ui-sortable-placeholder::after {
  content: '!';
  visibility: hidden;
}

.selectize-control.plugin-drag_drop .ui-sortable-helper {
  -webkit-box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
          box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

.selectize-dropdown-header {
  position: relative;
  padding: 5px 8px;
  background: #f8f8f8;
  border-bottom: 1px solid #d0d0d0;
  -webkit-border-radius: 3px 3px 0 0;
     -moz-border-radius: 3px 3px 0 0;
          border-radius: 3px 3px 0 0;
}

.selectize-dropdown-header-close {
  position: absolute;
  top: 50%;
  right: 8px;
  margin-top: -12px;
  font-size: 20px !important;
  line-height: 20px;
  color: #303030;
  opacity: 0.4;
}

.selectize-dropdown-header-close:hover {
  color: #000000;
}

.selectize-dropdown.plugin-optgroup_columns .optgroup {
  float: left;
  border-top: 0 none;
  border-right: 1px solid #f2f2f2;
  -webkit-box-sizing: border-box;
     -moz-box-sizing: border-box;
          box-sizing: border-box;
}

.selectize-dropdown.plugin-optgroup_columns .optgroup:last-child {
  border-right: 0 none;
}

.selectize-dropdown.plugin-optgroup_columns .optgroup:before {
  display: none;
}

.selectize-dropdown.plugin-optgroup_columns .optgroup-header {
  border-top: 0 none;
}

.selectize-control.plugin-remove_button [data-value] {
  position: relative;
  padding-right: 24px !important;
}

.selectize-control.plugin-remove_button [data-value] .remove {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  display: inline-block;
  width: 17px;
  padding: 2px 0 0 0;
  font-size: 12px;
  font-weight: bold;
  color: inherit;
  text-align: center;
 ...

JavaScript

$('select').selectize();

// Should make option 2 unselectable
$('select')[0].selectize.$dropdown_content.find('[data-value="2"]').removeAttr('data-selectable');